To the Editor.—The purpose of this letter is to add some important statements to my letter to the editor (227:658, 1974).Some of the most interesting and yet ignored evidence to support the possible link between the sudden death of sensitive asthmatic patients and the cardiac toxicity of the propellants could be found in the work of Dollery et al1 and Paterson et al.2 They reported that a concentration of 1.7μg/ml of trichloromonofluoromethane (Freon 11 [F 11]) was achieved in a patient after three puffs of isoproterenol sulfate (Medihaler-Iso) and 2.6μg/ml of F 11 in a patient only after two puffs of albuterol (Ventolin Inhaler). From these values one can estimate that inhalation of only 18 puffs of albuterol and 36 puffs of isoproterenol sulfate in these patients may build up blood concentrations up to 20μg to 25μg/ml of F 11, which were found capable of sensitizing